1. Field of the Invention
The present invention relates generally to semiconductor wafer polishing apparatus and, more specifically, a conditioning assembly for a polishing pad of a semiconductor wafer.
2. Discussion of Related Art
Semiconductor chips are manufactured by forming consecutive layers on a semiconductor wafer substrate. Raised and recessed formations can create undulations in a film. The undulations have to be planarized to allow for further fabrication.
Layers are usually polished in a process known in the art as “chemical-mechanical polishing” (CMP). CMP generally involves the steps of placing a wafer on a polishing pad with the layer to be polished on an interface between the wafer and the polishing pad. The wafer and the polishing pad are then moved over one another. A slurry is introduced on the polishing pad. The polishing pad has a textured surface so that movement of the wafer and the polishing pad over one another, in conjunction with the slurry, results in a gradual polishing of the layer.
After polishing a certain number of wafers, the material of the slurry and of the wafer eventually build up on the polishing pad so that the polishing pad becomes smooth. The smoothing of the polishing pad lessens the effectiveness on the surface of the wafer, resulting in a decrease in the polishing rate, or uneven polishing over the surface of the wafer. Therefore, conditioning of the polishing pad must occur.
The polishing pad is subsequently conditioned to redistribute the slurry. A conditioning assembly is moved over the surface of the polishing pad, contacting the surface of the polishing pad with a downward force. The conditioning of the polishing pad generates grooves therein, roughening the polishing pad and allowing for the effective removal of excess material, restoring the polishing feature of the polishing pad.